Compact loop question
 

I am in the process of constructing a compact loop for 80 meters. The loop
is constructed from 3/4 inch copper pipe in the shape of an octagon with a
perimeter of 72 feet, and the plane of the loop is vertical. According to
the literature, a loop of this type usually has a remotely tuned capacitor
in series with the top side of the loop, and the loop is feed at the bottom
with a gamma match.

For mechanical stability reasons, I would like to have the tuning capacitor
at the bottom of the loop, and feed the loop at the top of the loop. The
coax would be constrained to lie in the plane of the loop and would drop
vertically from the top of the loop to the ground. What disadvantages, if
any, are there to this second method of loop construction?

For more details of my project, see http://tinyurl.com/bwobb

Compact loop question
 

On Sun, 05 Mar 2006 22:41:54 GMT, "John, N9JG"
wrote:

What disadvantages, if
any, are there to this second method of loop construction?

Hi John,

What advantage is there in climbing a ladder to place the loop? Put
it at the bottom too.

73's
Richard Clark, KB7QHC

Compact loop question
 

I am not sure what you are recommending - Are you suggesting I make the
plane of the loop horizontal?
-- John

"Richard Clark" wrote in message
...
[snip]

Hi John,

What advantage is there in climbing a ladder to place the loop? Put
it at the bottom too.

73's
Richard Clark, KB7QHC

Compact loop question
 

On Mon, 06 Mar 2006 00:15:21 GMT, "John, N9JG"
wrote:

I am not sure what you are recommending - Are you suggesting I make the
plane of the loop horizontal?

no

What advantage is there in climbing a ladder to place the loop? Put
it at the bottom too.

73's
Richard Clark, KB7QHC

Compact loop question
 

On Mon, 06 Mar 2006 00:15:21 GMT, "John, N9JG"
wrote:

I am not sure what you are recommending - Are you suggesting I make the
plane of the loop horizontal?

Hi John,

A second loop driven by the coax placed in the same plane as your
larger one - and at the bottom. No reason to be fooling around at the
top of the arc of the big loop. No reason to break the big loop to
drive it.

73's
Richard Clark, KB7QHC

Compact loop question
 

Well, my problem is in deterring the antecedent for the "it" in your
suggestion. Are you recommending that both the tuning capacitor and the
feedpoint should be at the bottom of the loop? Please enlighten me.

Thanks, John

"Richard Clark" wrote in message
...
On Mon, 06 Mar 2006 00:15:21 GMT, "John, N9JG"
wrote:

I am not sure what you are recommending - Are you suggesting I make the
plane of the loop horizontal?

no

What advantage is there in climbing a ladder to place the loop? Put
it at the bottom too.

73's
Richard Clark, KB7QHC

Compact loop question
 

Now I understand your suggestion. Reg also recommends this method of
feeding, but the mechanics of mounting the second loop concerns me.

"Richard Clark" wrote in message
...
On Mon, 06 Mar 2006 00:15:21 GMT, "John, N9JG"
wrote:

I am not sure what you are recommending - Are you suggesting I make the
plane of the loop horizontal?

Hi John,

A second loop driven by the coax placed in the same plane as your
larger one - and at the bottom. No reason to be fooling around at the
top of the arc of the big loop. No reason to break the big loop to
drive it.

73's
Richard Clark, KB7QHC

Compact loop question
 

On Mon, 06 Mar 2006 13:27:19 GMT, "John, N9JG"
wrote:

the mechanics of mounting the second loop concerns me.

Very simple. Build a loop out of coax 1/5 the size of the main loop.
Make it out of the drive line by attaching the center conductor to the
shield at the point of full circumference. Put the loop inside the
main loop, co-planar, anywhere that conveniently suits you (I cannot
imagine a reason to climb a ladder to the top of the arc to do this,
though). Reggie's correspondence is more complete than this if you
can find it among his leavings in the archive.

73's
Richard Clark, KB7QHC

Compact loop question
 

As you describe it, it does seem to be simple. But, the inner loop is made
from coax and is flexible. Now I do plan to have a fiberglass pole, in the
plane of the loop, which will connect the top and the bottom of the loop so
as to give some rigidity to the outer loop. Perhaps this pole can also
partially support the inner loop. In any case I do appreciate your advice
and comments.
-- John

"Richard Clark" wrote in message
...
On Mon, 06 Mar 2006 13:27:19 GMT, "John, N9JG"
wrote:

the mechanics of mounting the second loop concerns me.

Very simple. Build a loop out of coax 1/5 the size of the main loop.
Make it out of the drive line by attaching the center conductor to the
shield at the point of full circumference. Put the loop inside the
main loop, co-planar, anywhere that conveniently suits you (I cannot
imagine a reason to climb a ladder to the top of the arc to do this,
though). Reggie's correspondence is more complete than this if you
can find it among his leavings in the archive.

73's
Richard Clark, KB7QHC